1. Field of the Invention
The present invention relates to a digital broadcasting receiving system connected to an MPEG-2 (Moving Picture Experts Group-2) equipment, such as a VOD (Video On Demand) server, having different data transmission rates, and more particularly to an asynchronous transport receiver used in a digital broadcasting receiving system based on a DVB-ASI (Digital Video Broadcasting Asynchronous Serial Interface) mode and its related method of transmitting asynchronous transport stream of the receiver.
2. Description of the Related Art
The standards for the serial transmission of a transport stream between various types of broadcasting equipments associated with the digital television broadcasting in a synchronous or asynchronous mode includes, for example, a SMPTE 310 (Society of Motion Picture and Television Engineers 310) mode, which is preferred in domains belonging to ATSC (Advanced Television System Committee), and a DVB-ASI (Digital Video Broadcasting-Asynchronous Serial Interface) mode, which is favored in domains provided with DVB (Digital Video Broadcasting) services.
FIG. 1 is a block diagram showing the construction of a transport stream receiver based on the conventional DVB-ASI mode. As shown, the conventional stream receiver includes a serial/parallel converter 10, an output FIFO (First-In First-Out) section 16, a synchronization sensor 11, a frame producer 12, a frame controlling and clock synchronizing section 13, a 27 MHz oscillator 14, and a 10-bit/8-bit converter 15.
In operation, the serial/parallel converter 10 converts serial 10-bit data inputted from the outside source into corresponding parallel 10-bit data. The synchronization sensor 11 senses a K28.5 synchronous byte from the converted 10-bit data. The K28.5 synchronous byte is stuffing datum that is inserted for the synchronization. The frame producer 12 reconstructs a frame from the parallel 10-bit data based on the detection of the K28.5 synchronous byte.
Meanwhile, the frame controlling and clock synchronizing section 13 controls the frame producer 12 for the synchronization using the clock signals of the 27 MHz oscillator 14. The 10-bit/8-bit converter 15 then converts the parallel 10-bit data into parallel 8-bit data, so that MPEG-2 data are outputted at the same line together with stuffing characters. Valid signals are generated and used to distinguish the MPEG-2 data from the stuffing characters. For instance, it is recognized that the MPEG-2 data is outputted when the valid signals are in a low state, but the stuffing characters are outputted when the valid signals are in a high state.
Note that when 270 MBaud serial data is converted into parallel data by the serial/parallel converter 10, the 270 MBaud serial data is converted into 27 MB/sec parallel data. Among the 27 MB/sec data outputted, the actual pure data are outputted at about 20 Mbps or less, except for the datum (K28.5 synchronous byte) that is actually subjected to the stuffing for synchronization. Accordingly, the output FIFO section 16 functions as a buffer for decreasing and outputting only the pure data components at about 6 Mbps or less through the removal of the K28.5 synchronous byte.
However, the conventional DVB-ASI transport stream receiver as described in the preceding paragraphs can only process the data in which the bit rate is less than about 20 Mbps. Therefore, when a high quality of image data, which belong to the level of high definition (HD), in particular in the bit rate of 50 Mbps or more, is to be outputted, it is necessary to provide an additional high frequency clock generator and a control circuit for controlling the clock generator. Thus, the conventional receiver has a disadvantage in that its construction becomes complicated.